The field of the present invention relates to a method for fastening securely by a simple procedure soft, porous tubes and other parts which are soft as a result of being made porous.
The present invention may be used as a method for fastening soft parts such as porous resin tubes which are used for purposes of filtration, degassing or addition of active ingredients. By "porous" is meant gas permeable but not liquid permeable.
When a synthetic resin material, such as a paste molding of a tetrafluoroethylene resin is subjected to a rolling or drawing treatment, the structure of the material is made porous. In this way, a special structure which is permeable to gases but impermeable to liquids can be obtained. By using a part, such as a tube made from such a material, it is possible to remove gas components from liquids (degassing) or to add gases to liquids (gas diffusion). Of course, various types of filtration can be smoothly accomplished using such a tube.
However, in the case of such parts, such as tubes, the synthetic resin may have a porosity of 70% or greater (80% or greater in some cases). accordingly such parts are extremely soft. When such soft parts are fastened to degassing or gas diffusion mechanisms of the type described above, it is necessary to fasten the end portions of said parts to said mechanisms. This fastening is accomplished by screw-tightening using tube connectors and the like.
In order to perform an efficient degassing or gas diffusion treatment using the above tubes, it is desirable that the tubes themselves have a small diameter. However, in cases where such small-diameter tubes are fastened using the aforementioned tube connectors. said connectors have a relatively large external diameter, i.e. a diameter that is approximately five times the external diameter of the tubes. Furthermore, in order to fasten the tubes, it is necessary to apply a tool such as a spanner or monkey wrench to the connectors and to manipulate the tool. Accordingly, a space sufficient for the manipulation of such a tool must be left between adjacent connectors. As a result, the space required for the fastening of a single tube is unavoidably large. For example, in a case where tubes with an internal diameter of 2 mm. and an external diameter of 3 mm. are fastened, the maximum number of tubes that can be fastened to a flat fastening seat with a diameter of 140 mm. is twenty-five.
Furthermore, in cases where such tubes are fastened as is by bonding with an adhesive, the setting of the adhesive causes a shrinkage of the tube diameter, so that an appropriate bonding strength cannot be obtained. As a result, gaps may be created so that leakage occurs.
Accordingly, although connectors must be used in order to insure stable fastening, the need for space limits the number of tubes that can be installed per unit area to a small number. As a result, the benefits of efficient treatment and a compact apparatus cannot be achieved.